Visible to Intel only — GUID: wns1522351179892
Ixiasoft
Visible to Intel only — GUID: wns1522351179892
Ixiasoft
7.1.1. Link Layer
In the Link Layer, the Condition Detector block shifts the serial data bus in (receive) and out (transmit) in eSPI clock domain. The input serial data is translated into parallel form and sent to transaction layer. The parallel data bus from the transaction layer is translated into serial form in the condition detector and sent out as the eSPI output data.
During the single I/O mode, the espi_data[1:0] I/O pins are unidirectional to form an unidirectional data bus. Data is driven using espi_data[0] during the command phase, and espi_data[1] the during response phase. The eSPI agent is required to tri-state espi_data[1] during command phase as espi_data[1] can be driven by eSPI host such as when initiating an In-Band Reset command.
During the dual I/O mode, the espi_data[1:0] I/O pins are bi-directional to form a bi-directional data bus. All the command and response phases are transferred over the two bidirectional pins at the same time, which effectively doubles the transfer rate than that of the single I/O mode.
During the quad I/O mode, the espi_data[3:0] I/O pins are bi-directional data bus. All the command and response phases are transferred over the four bi-directional pins at the same time, which effectively doubles the transfer rate than that of the dual I/O mode.
- Header (length and address): Most Significant Byte (MSB) to Least Significant Byte (LSB)
- Data: LSB to MSB
- Status: LSB to MSB